Field of the Disclosure
The present disclosure relates to a display device, and more particularly, to an organic light emitting display capable of compensating for characteristics of the driving TFTs driving organic-emitting pixels in a structure in which the pixels shares gate lines.
Description of the Background
An active matrix type organic light emitting display is an organic light emitting diode (hereinafter, referred to as “OLED”) which emits light by itself, and has advantages in fast response , high light emitting efficiency, high brightness, and wide viewing angle.
An organic light emitting display device includes pixels each including an OLED and a driving TFT (Thin Film Transistor) in a matrix form, and adjusts the luminance of an image implemented in a pixel according to gradation of video data. The driving TFT controls the driving current flowing in the OLED according to the voltage applied between the gate electrode and the source electrode of the driving TFT. The emission amount of the OLED is determined according to the driving current, and the brightness of the image is determined according to the emission amount of the OLED.
When the driving TFT operates in the saturation region, the pixel current flowing from the drain to the source of the driving TFT changes depending on the electrical characteristics of the driving TFT, such as a threshold voltage and an electron mobility. The electrical characteristics of the driving TFTs vary between pixels due to various causes such as process characteristics and time-varying characteristics, and thus even if the same data voltage is applied to pixels having different electrical characteristics of TFTs, luminance deviations can occur between the pixels. So, unless the characteristic deviations are compensated, it is difficult to realize images with desired quality.
In order to solve such a problem, there has been proposed a technique of compensating for a luminance deviation due to a deviation of electrical characteristics (e.g., threshold voltage, mobility) of driving TFTs within pixels and/or outside pixels. An internal compensation manner has a disadvantage that a pixel structure is complicated and an aperture ratio becomes low. On the other hand, an external compensation manner, which senses the characteristic parameters of the driving TFTs of individual pixels and corrects input data according to the sensing values, takes a long time for sensing.
Recently, a hybrid compensation manner has been proposed in which a pixel structure is simplified and a sensing time is reduced by compensating the luminance non-uniformity due to the threshold voltage deviation of the driving TFTs by the external compensation manner, and compensating the luminance non-uniformity due to the mobility deviation of the driving TFTs by the internal compensation manner.
Meanwhile, as the resolution of a mobile device such as a smart phone increases, the number of pixels increases compared to a panel size, which results in the problems such as a complicated pixel structure and a reduction in free space in a bezel. In order to solve these problems, there is a tendency to adopt a structure, for reducing the number of channels of a source drive IC (Integrated Circuit), in which gate lines of a k-th line and a (k+1)-th line are shared and/or one channel supplies data voltages to two sub-pixels adjacent in a horizontal direction.
However, when the structure sharing gate lines or sharing a channel of a data driving circuit is applied to an organic light emitting display, the hybrid compensation scheme for solving the luminance non-uniformity problem inherent in the organic light emitting display cannot be realized.